Optical multiplexing1,2,3,4,5,6,7,8,9,10,11 by creating orthogonal data channels has offered an unparalleled approach for information encoding with substantially improved density and security. Despite the fact that the orbital angular momentum (OAM) of light involves physical orthogonal division, the lack of explicit OAM sensitivity at the nanoscale prevents this feature from realizing nanophotonic

X-ray and gamma-ray photons are widely used for imaging but require a mathematical reconstruction step, known as tomography, to produce cross-sectional images from the measured data. Theoretically, the back-to-back annihilation photons produced by positron–electron annihilation can be directly localized in three-dimensional space using time-of-flight information without tomographic reconstruction;

Quantum teleportation, the faithful transfer of an unknown input state onto a remote quantum system1, is a key component in long-distance quantum communication protocols2 and distributed quantum computing3,4. At the same time, high-frequency nano-optomechanical systems5 hold great promise as nodes in a future quantum network6, operating on-chip at low-loss optical telecom wavelengths with long mechanical

Waveplates are widely used in photonics to control the polarization of light1,2. Often, they are fabricated from birefringent crystals that have different refractive indices along and normal to the crystal axis. Similar optical components are found in the natural world, including the eyes of mantis shrimp3,4 and the iridescence of giant clams5, fish6 and plants7. Optical retardation in biology relies

The phase of terahertz waves can now be precisely modulated electronically using a chip-based digitally coded phase shifter. The achievement is a step towards chip-scale integrated terahertz technology.

News of a 1.3-MJ-output-energy experiment at the National Ignition Facility in the United States in August has raised hopes that laser-based fusion is back on track.

Time-varying metamaterials bring in an extra degree of freedom, enabling applications unachievable by normal metamaterials and opening up new opportunities.

Solution-processed semiconductor lasers have achieved much success across the nanomaterial research community, including in relation to organic semiconductors1,2, perovskites3,4 and colloidal semiconductor nanocrystals5,6. The ease of integration with other photonic components and the potential for upscaling using emerging large-area fabrication technologies (such as roll-to-roll7) make these lasers

Research into organic light emitters employing multiple resonance-induced thermally activated delayed fluorescence (MR-TADF) materials is presently attracting a great deal of attention due to the potential for efficient deep-blue emission. However, the origins and mechanisms of successful TADF are unclear, as many MR-TADF materials do not show TADF behaviour in solution, but only as particular pure

In free-space optical communications that use both amplitude and phase data modulation (for example, in quadrature amplitude modulation (QAM)), the data are typically recovered by mixing a Gaussian local oscillator with a received Gaussian data beam. However, atmospheric turbulence can induce power coupling from the transmitted Gaussian mode to higher-order modes, resulting in a significantly degraded

Cavity solitons are optical pulses that propagate indefinitely in nonlinear resonators. They are attracting attention, both for their many potential applications and their connection to other fields of science. Cavity solitons differ from laser dissipative solitons in that they are coherently driven. So far the focus has been on driving Kerr solitons externally, at their carrier frequency, in which

Upconversion nanocrystals have been extensively investigated for optical imaging and biomedical applications1,2. However, their photoluminescence is strongly attenuated by surface quenching as the nanocrystal size diminishes3. Despite considerable efforts4,5, the quenching mechanism remains poorly understood. Here we report that surface coordination of bidentate picolinic acid molecules to NaGdF4:Yb/Tm

Second-harmonic generation is of paramount importance in several fields of science and technology, including frequency conversion, self-referencing of frequency combs, nonlinear spectroscopy and pulse characterization. Advanced functionalities are enabled by modulation of the harmonic generation efficiency, which can be achieved with electrical or all-optical triggers. Electrical control of the harmonic

Perovskite nanocrystals are exceptional candidates for light-emitting diodes (LEDs). However, they are unstable in the solid film and tend to degrade back to the bulk phase, which undermines their potential for LEDs. Here we demonstrate that perovskite nanocrystals stabilized in metal–organic framework (MOF) thin films make bright and stable LEDs. The perovskite nanocrystals in MOF thin films can maintain

Photon propagation through an array of coupled waveguides arranged in various fractal patterns serves as a useful ‘optical simulator’ for revealing insights into quantum transport in complex scenarios.

Nature Photonics spoke to Chihaya Adachi from the Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, about the potential merits of, and hurdles facing, the development of organic semiconductor lasers.

Franky So, from North Carolina State University, explains some hard truths for solution-processed emitters, but also that, fundamentally, there is no reason why OLEDS can’t ‘make it’.

A simple yet effective optical set-up, employing two controllable, indistinguishable photons, is proven to allow a direct measurement of the exchange phase due to the bosonic particle statistics.

Solution-processing of light-emitting devices is attracting much attention due to low manufacturing costs and access to new materials. In this month’s Focus issue we highlight some of the advances and challenges in the field.

Low stability of perovskite light-emitting diodes (PeLEDs) is the biggest obstacle to the commercialization of PeLED displays. Here, we cover the current status and challenges in analysing and improving the stability of PeLEDs and suggest some advice that will benefit the community to boost the operational lifetime of PeLEDs.

Near-infrared light-emitting diodes based on solution-processed semiconductors, such as organics, halide perovskites and colloidal quantum dots, have emerged as a viable technological platform for biomedical applications, night vision, surveillance and optical communications. The recently gained increased understanding of the relationship between materials structure and photophysical properties has

Colloidal quantum dots (QDs) combine the superior light-emission characteristics of quantum-confined semiconductors with the chemical flexibility of molecular systems. These properties could, in principle, enable solution-processable laser diodes with an ultrawide range of accessible colours. However, the realization of such devices has been hampered by fast optical gain decay due to non-radiative

Electromagnetic confinement in optical resonators of diminishing dimensions has enabled unprecedented light–matter interaction strengths. This miniaturization trend has a nonlocal limit, which, surprisingly, originates from the matter excitations rather than the light.

Direct phase modulation is one of the most urgent and difficult issues in the terahertz research area. Here, we propose a new method employing a two-dimensional electron gas (2DEG) perturbation microstructure unit coupled to a transmission line to realize high-precision digital terahertz phase manipulation. We induce local perturbation resonances to manipulate the phase of guided terahertz waves. By

Subwavelength electromagnetic field localization has been central to photonic research in the last decade, allowing us to enhance sensing capabilities as well as increase the coupling between photons and material excitations. The strong and ultrastrong light–matter coupling regime in the terahertz range using split-ring resonators coupled to magnetoplasmons has been widely investigated, achieving successive

The conversion efficiency of solar energy in semiconductors is fundamentally limited by ultrafast hot-carrier relaxation processes, and slowing down these processes is critical for improved energy harvesting. Here we report formamidinium tin iodide (FASnI3) nanocrystals where quantum confinement effects yield an evolution from a continuous band structure to separate energy states with decreasing nanocrystal

There has recently been growing interest in integrating and miniaturizing vapour cells to reduce cost, size and power consumption. Hereby we provide a new paradigm in chip-scale-integrated vapour cells by experimentally demonstrating the nanoatomic suspended waveguide, which introduces a nanoscale silicon nitride waveguide suspended in rubidium vapour. By doing so, the properties of the optical modes

Terahertz radiation has become an important diagnostic tool in the development of new technologies. However, the diffraction limit prevents terahertz radiation (λ ≈ 0.01–3 mm) from being focused to the nanometre length scale of modern devices. In response to this challenge, terahertz scanning probe microscopy techniques based on coupling terahertz radiation to subwavelength probes such as sharp tips

The 2014 Nobel laureate, Isamu Akasaki, sadly passed away in April at the age of 92. He was highly regarded for his work on the invention of efficient blue light-emitting diodes and research into new semiconductor materials.

Recent years have witnessed a much broader use of Brillouin inelastic light-scattering spectroscopy for the investigation of phonons and magnons in novel materials, nanostructures and devices. Driven by the developments in instrumentation and the strong need for accurate knowledge on the energies of elemental excitations, Brillouin–Mandelstam spectroscopy is rapidly becoming an essential technique

Fractals are fascinating, not only for their aesthetic appeal but also for allowing the investigation of physical properties in non-integer dimensions. In these unconventional systems, many intrinsic features might come into play, including the fractal dimension and the fractal geometry. Despite abundant theoretical studies, experiments in fractal networks remain elusive. Here we experimentally investigate

The adiabatic encirclement of exceptional points in non-Hermitian systems is known to produce surprising non-adiabatic effects. A new study finds a cheat code to exactly emulate this behaviour without ever having to produce an exceptional point.

Reducing the footprint of optical spectrometers is a critical requirement for many in-field applications. Now, a single black phosphorus photodetector with a wavelength-scale size enables mid-infrared computational spectrometry.

A ‘twin-field’ repeater-less protocol has enabled an experimental demonstration of secure quantum key distribution over a 511-km long-haul optical fibre link.

Laser-induced electron tunnelling—which triggers a broad range of ultrafast phenomena such as the generation of attosecond light pulses, photoelectron diffraction and holography—has laid the foundation for strong-field physics and attosecond science. Using the attoclock constructed by single-colour elliptically polarized laser fields, previous experiments have measured the tunnelling rates, exit positions

Metal halide perovskite solar cells have demonstrated a high power conversion efficiency (PCE), and further enhancement of the PCE requires a reduction of the bandgap-voltage offset (WOC) and the non-radiative recombination photovoltage loss (ΔVOC,nr). Here, we report an effective approach for reducing the photovoltage loss through the simultaneous passivation of internal bulk defects and dimensionally

Light with spatiotemporal orbital angular momentum (ST-OAM) is a recently discovered type of structured and localized electromagnetic field. This field carries characteristic space–time spiral phase structure and transverse intrinsic OAM. Here, we present the generation and characterization of the second harmonic of ST-OAM pulses. We uncover the conservation of transverse OAM in a second-harmonic generation

A chip-based optical frequency comb has enabled the realization of a 300 GHz signal with record low phase noise. The development could yield ultra-compact, ultra-low-noise sources for millimetre-wave applications in telecommunications, remote sensing and precision spectroscopy.

Dynamic control over the conduction band electrons of a semiconductor is a central technological pursuit. Beyond electronic circuitry, flexible control over the spatial and temporal character of semiconductor currents enables precise spatiotemporal structuring of magnetic fields. Despite their importance in science and technology, the control of magnetic fields at the micrometre spatial scale and femtosecond

The basic principle of quantum mechanics1 guarantees the unconditional security of quantum key distribution (QKD)2,3,4,5,6 at the cost of forbidding the amplification of a quantum state. As a result, and despite remarkable progress in worldwide metropolitan QKD networks7,8 over the past decades, a long-haul fibre QKD network without a trusted relay has not yet been achieved. Here, through the sending-or-not-sending

Light–matter interactions can create and manipulate collective many-body phases in solids1,2,3, which are promising for the realization of emerging quantum applications. However, in most cases, these collective quantum states are fragile, with a short decoherence and dephasing time, limiting their existence to precision tailored structures under delicate conditions such as cryogenic temperatures and/or

Precision optical-frequency and phase synchronization over fibre is critical for a variety of applications, from timekeeping to quantum optics. Such applications utilize ultra-coherent sources based on stabilized table-top laser systems. Chip-scale versions of these systems may dramatically broaden the application landscape by reducing the cost, size and power of such exquisite sources. Links based

Anderson’s groundbreaking discovery that the presence of stochastic imperfections in a crystal may result in a sudden breakdown of conductivity1 revolutionized our understanding of disordered media. After stimulating decades of studies2, Anderson localization has found applications in various areas of physics3,4,5,6,7,8,9,10,11,12. A fundamental assumption in Anderson’s treatment is that no energy

The unique optical properties of graphene were combined with lithium-ion battery technology to produce multispectral optical devices, with colour-changing capabilities.

Parity–time reversal symmetry (PT symmetry) in non-Hermitian systems realizes spontaneous symmetry breaking, thereby leading to counterintuitive phenomena. A coupled system with antisymmetric gain/loss profiles is required to introduce PT symmetry into photonics. As photons are intrinsically non-interactive, selection of two-photonic components is inevitable to mediate indirect coupling via near-fields

Short period, femtosecond transient gratings in a sample can now be produced by X-rays. The approach promises to reveal the excitation behaviour of complex materials with high temporal and spatial resolution.

Webb’s work helped fundamentally reshape basic research and advanced manufacturing in the generation and application of photonics across disciplines, from fundamental and applied physics to the biosciences.

Twin-field (TF) quantum key distribution (QKD) fundamentally alters the rate-distance relationship of QKD, offering the scaling of a single-node quantum repeater. Although recent experiments have demonstrated the new opportunities for secure long-distance communications allowed by TF-QKD, formidable challenges remain to unlock its true potential. Previous demonstrations have required intense stabilization

Quantum theory stipulates that if two particles are identical in all physical aspects, the allowed states describing the system are either symmetric or antisymmetric with respect to permutations of single-particle states1,2,3,4,5. Experimentally, the symmetry of the states can be inferred indirectly from the fact that neglecting the correct exchange symmetry in the theoretical analysis leads to dramatic

On-chip polarization-sensitive photodetectors offer unique opportunities for next-generation ultra-compact polarimeters. So far, mainstream approaches have relied on the anisotropic absorption of natural materials or artificial structures. However, such a model is inherently restricted by correlation between the polarization ratio (PR) and diattenuation, leading to small PR values (1 < PR < 10). Here

Over the past decade, metal halide perovskite photovoltaics have been a major focus of research, with single-junction perovskite solar cells evolving from an initial power conversion efficiency of 3.8% to reach 25.5%. The broad bandgap tunability of perovskites makes them versatile candidates as the subcell in a tandem photovoltaics architecture. Stacking photovoltaic absorbers with cascaded bandgaps

In 1982, Capasso and co-workers proposed the solid-state analogue of the photomultiplier tube, termed the staircase avalanche photodiode. Through a combination of compositional grading and small applied bias, the conduction band profile is arranged into a series of steps that function similar to the dynodes of a photomultiplier tube, with twofold gain arising at each step via impact ionization. A single-step

Free-electron lasers producing ultrashort pulses with high peak power promise to extend ultrafast non-linear spectroscopic techniques into the extreme-ultraviolet–X-ray regime. Key aspects are the synchronization between pump and probe, and the control of the pulse properties (duration, intensity and coherence). Externally seeded free-electron lasers produce coherent pulses that can be synchronized

Tunnelling currents inside plasmonic nanostructures are fast enough to gain direct access to the oscillating electric field of near-infrared and visible light, opening up exciting routes towards attosecond metrology of light–matter interaction and unique approaches to spectroscopy.

The successful demonstration of two-stage acceleration driven by terahertz pulses bodes well for the future development of compact, efficient particle accelerators.

Tunnelling is one of the most fundamental manifestations of quantum mechanics. The recent advent of lightwave-driven scanning tunnelling microscopy has revolutionized ultrafast nanoscience by directly resolving electron tunnelling in electrically conducting samples on the relevant ultrashort length- and timescales. Here, we introduce a complementary approach based on terahertz near-field microscopy

A new way to define the shape of tiny light-emitting semiconductor pixels provides a means to fabricate arrays of InGaN blue micro-LEDs with a resolution as high as 8,500 pixels per inch.

Optical frequency combs are lightwaves composed of a large number of equidistant spectral lines. They are important for metrology, spectroscopy, communications and fundamental science. Frequency combs are most often generated by exciting dissipative solitons in lasers or in passive resonators, both of which suffer from important limitations. Here we show that the advantages of each platform can be

Sources of quantum light, in particular correlated photon pairs that are indistinguishable for all degrees of freedom, are the fundamental resource for photonic quantum computation and simulation. Although such sources have been recently realized using integrated photonics, they offer limited ability to tune the spectral and temporal correlations between generated photons because they rely on a single

One of the most fascinating aspects of quantum networks is their capability to distribute entanglement as a nonlocal communication resource1. In a first step, this requires network-ready devices that can generate and store entangled states2. Another crucial step, however, is to develop measurement techniques that allow for entanglement detection. Demonstrations for different platforms3,4,5,6,7,8,9